To assess the usefulness and efficacy of low-dose Bupivacaine with Fentanyl spinal

anesthesia for prevention of hypotension while maintaining good anesthetic

conditions.

Patients and Methods

At Prince Rashid Hospital, 100 adult patients were randomized into two groups. The

study group (F) comprised of 50 patients who received spinal anesthesia with

Bupivacaine 7.5-9mg and fentanyl 25 µg, while in control group (B), 50 patients

received Bupivacaine 12.5-15mg only. The homodynamic stability of the patients and

the quality of the blocks were compared.

Results

All patients had adequate duration of reliable blocks. More control group patients than

study group patients required ephedrine due to hypotension.

Conclusion

A reduced dose of Bupivacaine in combination with fentanyl provided reliable spinal

anesthesia with few events of hypotension and little need for vasopressor support for

blood pressure. (Rawal Med J 2011;36:116-119).

Key words

Bupivacaine, fentanyl, spinal anesthesia.

INTRODUCTION

The ideal spinal anesthesia for ambulatory surgery should provide good surgical anesthesia with rapid recovery from sensory and motor block. 1Lignocaine has been

widely advocated for ambulatory anesthesia but many studies have questioned the use

of hyperbaric 5% lignocaine for spinal anesthesia and recommended consideration of

bupivacaine as a substitute. 2Bupivacaine, an amide type of local anesthetic, has high potency, slow onset (5–8 minutes) and long duration of action (1.5–2 hours). Although spinal anesthesia is safe but it is not devoid of complication, hypotension and sinus bradycardia are the most complication and are attributed to the imbalance between sympathetic and parasympathetic control of the heart rate. Stimulation of the sympathetic system may induce myocardial ischemia by causing coronary vasoconstriction 3and may be related to the genesis of ventricular tachyarrhythmia. 4Hypotension after spinal anesthesia is often treated with vasopressors and intravenous fluids. This regime is controversial for the geriatric population with coronary disease 5may increase risk of pulmonary oedema in high-risk pregnant patients and has been associated with fetal acidosis. 6Bupivicaine has other side effects like increased motor block and bladder dysfunction leading to delayed discharge. 7

There has been controversy concerning the relationship between volume, concentration and total dose of spinally administered drugs. Most of the studies suggest that the total dosage is more important than the volume. 8These concerns have increased interest in the use of small doses of bupivacaine. 9Intrathecal opioids have been shown to enhance analgesia from sub therapeutic doses of local anesthetics and make it possible to achieve spinal anesthesia using otherwise inadequate doses of local anesthetic. 10,11In this study, we focused on the usefulness and efficacy of low- dose bupivacaine with fentanyl spinal anesthesia to prevent hypotension and other complications while maintaining good anesthetic conditions.

PATIENTS AND METHODS

This prospective study included 100 patients who underwent lower abdominal, anorectal, orthopedic and obstetric surgery under spinal anesthesia technique from February 2008 to December 2008 at Prince Rashid Hospital. Patients with a history of

previous back surgery, infection at the injection site, uncontrolled hypertension, hypersensitivity to amide local anesthetics or fentanyl, mental disturbance, or neurologic disease coagulation disorders were excluded from the study as well as patients who required conversion to general anesthesia. The approval of the Institutional Ethical Studies Committee was given for the study

Patients were divided into two group each group with fifty patients. In the first group (F), 7.5-9 mg of 0.5 percent heavy bupivcaine was injected intrathecaly plus 25 mu fentanyl. In the second group (B), 12.5-15 mg of 0.5 percent heavy bupivcaine only was injected intrathecaly. The study was randomized and double-blind regarding the anesthesia solution, with the subjects being assigned to a study group or a control group using a sealed-envelope technique.

No premedication was given. ECG, non-invasive blood pressure, heart rate and peripheral oxygen saturation were monitored. After an intravenous access was established the patients were received 500 ml of sodium chloride 0.9% solution over 30 min. The intravenous infusion was maintained at (8 ml/kg/1.h) during the intra- operative period. Oxygen was continuously given via a face mask. Systolic arterial pressure (SAP) and heart rate (HR) were recorded at 5 minute interval at the onset of block, then at 15 minute intervals until the resolution of the block. Hypotension (SAP <90 or 30% decrease from the baseline) was treated with intravenous bolus of ephedrine 3-6 mg, trendelenberg position by 15 degrees and administration of IV fluid 500-1000 ml of lactated range and bradycardia (HR <45) was treated with atropine 0.5 mg intravenously.

Sensory block was determined with a 22-gauge needle in the dermatome levels tested every two minutes from injection until the level established for four consecutive tests Testing was then conducted every 10 minutes until two segment regression. Further testing was then performed at 20 minute intervals in the recovery room until recovery of the S2 dermatome. Motor block was assessed with the Bromage scale (0 no motor block; 1 hip blocked; 2 hip and knee blocked; and 3 hip, knee and foot blocked). Duration of motor block was considered as the time when Bromage score returned to (0). Motor blockade was assessed at the time of reaching peak sensory level and this was considered the maximum motor blockade. Pain was assessed every 10 minutes from the beginning of surgery till discharge from recovery room using a 10-cm visual analogue pain scale, intra and postoperative analgesia consumption. It was treated with pethidine (1mg/kg) intramuscularly every 6 h when needed in the 1 st24 hours postoperatively. Adverse effects such as nausea, vomiting, shivering, pruritus, respiratory depression, and transient neurological symptoms were recorded.

RESULTS

There were 81 male and 19 female patients in this study; there ages ranged from 23 to

95 year (mean 56). Inguinal herniorrhaphy was the commonest surgery performed

(Table 1).

Table 1. Type of surgical procedures.

Procedure

Number

Inguinal hernia

39

Anorectal surgery

27

orthopedic surgery

27

Obstetric surgery

5

High ligation of varicose vein

2

Total

100

The sensory and motor block in the two groups is shown in Table 2.

Table 2. Sensory and motor block variables.

Variable

Group F

Group B

Numberof dermatomes blocked( mean)

13

11

Upper limit of sensory block

T12

T11

Time to reach peak of sensory block(minute)

8.6

9.1

Maximum motor block (Bromage scale 0-3) mean

1

2

Duration of motor block (minute)

110.6

134.4

Time of sensory regression (minute)

174

191.2

Two segment regression(minute)

55.4

64.4

The number of dermatomes blocked was relatively comparable in both groups as well as the median upper limit of the sensory block. Recovery of motor function took place significantly earlier in Group F compared with Group B (110.6 minute vs 134.4 minute).

Table 3. Pain variables.

Group

F

B

Number of patients needing intra-operative

8

9

analgesia (intravenous fentanyl)

Average pethidine dose post operatively

245

267

(mg) per patient

VAS (intra operative 0-10)

2.7

2.8

VAS (post operative 0-10)

5.1

4.9

Time to reach of peak sensory lose was earlier in group F, however did not differ significantly. Although the two-segment regression was slower in Group B compared with Group F but did not seemed to be significant, but time for sensory recovery was earlier in group F than group B, (174.3 minute vs 191.2 minute).

No differences were found between the groups in the total analgesic consumption

(Table 3), or the number of patients who required postoperative analgesics in the recovery room.

Table 4. Adverse effects.

Group

F

B

(number)

(number)

Hypotension

3

13

Total of

ephedrine doses

97.5

20.0

(mg)

Bradycardia

2

1

Nausea and vomiting

1

2

Shivering

1

2

Pruritus

3

1

Respiratory depression

0

0

Transient

neurological

0

0

manifestation

Lowest SAP (<30%) occurred in Group B (13 patients) and was significantly higher than those of Group F (3 patients), while incidence of bradycardia was comparable in both groups (Table 4). Total amount of the ephedrine used for treatment of hypotension was higher in Group B than Group F (97.5 mg vs 20mg respectively). Other adverse effects seem to be comparable in both groups except for pruritus that is higher in group F (Table 4).

DISCUSSION

Although spinal anesthesia is significantly safer than general anesthesia, morbidity

and mortality still can occurred with spinal anesthesia. Deaths in regional anesthesia

are primarily related to excessive high regional blocks and toxicity of local

anesthetics. Reduction in doses and improvement in technique to avoid higher block

levels and heightened awareness to the toxicity of local anesthetics have contributed

to the reduction of complications related with regional anesthesia. 12As bupivacaine is

used commonly for spinal and epidural anesthesia, we decided to combine it with

intrathecal fentanyl for various surgical procedures to provide adequate depth of

anesthesia with lesser doses of bupivacaine 13with better maintainance of the

hemodynamic stability of these patients.

Our results are comparable with those studies that proved the improvement of intrathecal opioids without altering the degree of sympathetic blockade when added to sub therapeutic doses of local anesthetics. 14,15It potentiates sensory anesthesia without prolonging recovery from spinal anesthesia. 16However, motor recovery was not significantly affected by the addition of intrathecal fentanyl.

Bradycardia results from the blockade of sympathetic cardio accelerator fibers and decreased venous return to the heart. In our study, bradycardia overall occurrence was 4 % (in F group) with no significant inter group variation, while incidence of hypotension was markedly reduced by lowering the anesthetic drug and adding intrathecal fentanyl. We should admit that the variation in our included surgical procedures limit us to specify our results for specific procedure but our results are comparable with various studies for single procedure.

CONCLUSIONS

A reduced dose of bupivacaine in combination with fentanyl provided reliable spinal anesthesia in adults for variable kinds of surgical procedures with few events of hypotension and little need for vasopressor support of blood pressure. It offers a reliable block, good post-operative analgesia and satisfactory for the patient and surgeon.